Determination of the growth stress and strain inα-Al2O3scales during the oxidation of Fe–22Cr–4.8Al–0.3Y alloy

Abstract

Abstract High temperature oxidation of rectangular plates of Fe–22%Cr–4.8%Al–0.3%Y (wt%) leads to an increase of their size. Measurements of the macroscopic elongational strain and the residual stress in the oxide (by piezospectroscopy) are compared as a function of oxidation time at temperatures 1100, 1200 and 1300°C. Analysis of the experimental results for plates of different initial thickness is used to determine the in-plane growth strain and the concurrent creep strain in the oxide during oxidation. The lateral growth strain in the α-Al 2O 3 scale is found to increase almost parabolically with oxidation time and increase with temperature. It is shown that creep of the oxide provides a significant additional stress relaxation concurrently with the metal lateral expansion. The relative contribution of these two relaxation processes depends on the metal–oxide thickness ratio.

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